Solenoid with enlarged plunger head



March 15, 1966 1. A. MORRIS, JR

SOLENOID WITH ENLARGED PLUNGER HEAD Filed Feb. 14, 1963 INVENTOR ISAAC A. MORRIS, JR. BY Z FIG. 3

ATTORNEYS United States Patent 3,241,005 SOLENOID WITH ENLARGED PLUNGER HEAD Isaac A. Morris, J12, Outlet Road, Clifton Springs, N.Y. Filed Feb. 14, 1963, Ser. No. 258,540 9 Claims. (Cl. 317191) This invention relates to an improved solenoid construction. A significant object of this invention is to provide axial alignment of the solenoid plunger substantially the entire length of the valve during reciprocation thereof, while at the same time providing an increased cross-sectional area of the plunger at the central zone of the magnetic flux pattern where there is greatest flux density, thereby appreciably increasing the pulling force applied to the plunger by the solenoid coil for the diameter of the plunger.

It is a further object of this invention to provide an improved solenoid construction of the above described nature which also eliminates possible damage to the plunger by inadvertent dislodgement from the solenoid coil or spool.

To applicants knowledge there has never, heretofore, been a solenoid which has completely and satisfactorily overcome the problems as the applicant has solved by the above recited objects.

In the past there have been many solenoid constructions designed to overcome the problems of wear and chatter during operation thereof resulting from poor alignment of the plunger during reciprocation within the solenoid coil. There are all variations of alignment bearing means intermediate the coil and the outside diameter of the plunger.

The most common type of known constructions comprise, a magnetic coil having a central opening extending theret-hrough provided with a cylindrical sleeve generally of non-magnetic material, extending the greater length of the central opening which sleeve and coil opening are closed at the upper end by a plunger stop. The plunger has been of uniform cross-section throughout substantially that portion of axial length being reciprocal in the sleeve of the coil opening. Sometimes the lower end of the plunger has been formed with a shoulder portion cooperating with a spring or other biasing means for yieldingly biasing the plunger to a normal position.

Perhaps the most significant object of my invention is to eliminate a small portion axially of the sleeve at the central, zone of the magnetic flux pattern where the flux density is greatest, thereby to define a working gap at the upper end of the sleeve of increased cross-section and provide an enlarged head portion on the internally disposed end of the solenoid plunger being shorter axially than the working gap provided at the upper end of the sleeve so the enlarged head of the plunger is reciprocal in the working gap. This construction greatly increases the effective electromagnetic pulling force on the plunger. The electromagnetic pulling force is increased by approximately the same percentage as the increased surfiace area of the plunger head for a given stroke and voltage. This construction also eliminates the commonly occurring inadvertent displacement of the plunger from the solenoid during assembly and disassembly with valve bodys or other apparatus with which the solenoid may be used.

One object of this invention is to provide an improved solenoid construction minimizing the cost and time necessary for assembly thereof.

Other objects and advantages of this invention will particularly be set forth in the claims and will be apparent from the following description, when taken in connection with the accompanying drawings, in which:

FIG. 1 is a top planar view of one embodiment of my ice invention; FIG. 2 is a section-a1 view taken along the line 2-2 of FIG. 1 loolcing in the direction indicated by the arrows; FIG. 3 is a bottom planar view of the embodiment illustrated in FIGS. 1 and 2.

In FIG. 1, I have illustrated a direct-current solenoid embodying the concept of my invention it being understood that my invention is adapted for use in alternating current solenoids. My construction includes a cylindrical coil or spool 10 encapsulated in a protective coating 15 of, for example, epoxy resin. Lead wires 12 of coil 10 are connected to a source of direct current. Coil 10 has a cylindrical opening 16 extending vertically through the center there-of.

I provide a solenoid headplate 18 of magnetic composition, having a radially extending flange 20. The upper surface of flange 20 is bonded to the lower surface 14 of the coil 10 as, for example, by epoxy adhesive. Headplate 18 is provided with a vertically extending cylindrical sleeve portion 22 being axially received inside of the central cylindrical opening 16 of the coil 10 from the lower end thereof. The outer surface of sleeve 22 is bonded to the lower portion of the interior surface of opening 16, as for example, by epoxy adhesive. Coil 10 and headplate 18 are received internally of an outside cylindrical housing or casing 24; the exterior surface of the coil 10 and headplate 18 are preferably bonded on the interior surface of the casing 24, as for example, by epoxy adhesive.

Casing 24 has a downwardly extending cylindrical portion 26 formed at the lower end thereof which is crimped as illustrated in FIG. 2 in order to secure the headplate 18 rigidly against a shouldered portion 27 of casing 24. A lower portion 28 of the headplate 18 is threaded at 30 for assembly with other apparatus, as for example a valve body.

The solenoid headplate 28 is provided with an interior central cylindrical bore 32 for slidably receiving a lower smaller in diameter body portion 34 of a solenoid plunger generally indicated by the numeral 36. Plunger 36 is provided with an upper larger in diameter head portion 38 shouldered on the upper end of sleeve 22. The enlarged head portion 38 in combination with the sleeve portion 22 of the headplate 18 extending axially into the coil opening 16 is a significant feature of my invention. This enlarged portion 38 of plunger 36 extends only a short distance axially as compared to the lower smaller in diameter portion 34.

The upper end of coil opening 16 is closed by a flanged stop member 39 having a vertically disposed cylindrical portion 44 extending a selected distance into the coil opening to define a working gap 41 between the lower end thereof and the upper end of heaclplate sleeve 22; the enlarged head 38 of the plunger is reciprocal within the axial limits defined by gap 41. Preferably, the outside circumference of the cylindrical portion 44 is bonded to the inside circumference of the core opening 16, as fior example, by an epoxy adhesive.

A radial flange portion 46 of the stop member 39 is rigidly secured within casing 24 against an upper inside shoulder 47 thereof by crimping an upper cylindrical portion 48 of the casing 24 90 in the same manner as illustrated at 26 at the lower end of the casing. The flange 46 of upper stop member 39 is provided with a pair of U-shaped openings 50 (FIG. 1) through which protrude a pair of cylindrical portions 52 of epoxy resin capsule 24 carrying lines 12.

I provide a pin 40 rigidly mounted at its lower end in a bore in the upper end of plunger 36, as for example, by press fitting or threading. The upper end of pin 40 is slidably received in a central axial bore 42 of flanged stop member 39.

Surrounding alignment pin 40 and slidable thereon is a thin circular spacer 54 having a slightly smaller outside diameter than the inside diameter 16 of the coil 10. Spacer 54 is made of non-magnetic stainless steel which functions to break any residual magnetism which would otherwise tend to maintain the plunger 36 in the elevated position (not shown) after electrical current has ceased to flow through the coil 10. Pin 40 maintains spacer 54 centrally of the bore 16 to prevent engagement of the edges of the spacer 54 on the bore 16, thereby preventing any sticking of the solenoid or distortion of the spacer 54.

Bore 42 of stop member 39 receives a compression coil spring 56 interposed between the upper end of alignment pin 40 and a dog point adjustable set screw 58 adjustable axially of a threaded portion 60 of the bore 42. By this construction, the plunger 36 is normally yieldingly biased by the compression coil spring 56 to the downward position illustrated in solid line in FIG. 2, in which position the shoulder of the enlarged head portion 38 of the plunger engages the upper end of the cylindrical sleeve 22. It will be understood that the set screw 58 may be adjusted to vary the biasing force being exerted by the compression coil spring 56 on the pin 40 and in turn the plunger 36. When the coil is energized, the plunger 36 is elevated, in opposition to spring 56, until the upper surface of spacer 54 engages the lower surface of stop member 39.

The plunger 36 is provided with an axially extending slot 62 providing an air passage through the plunger to the working gap 41 in which the upper enlarged head 38 of the plunger is reciprocal.

It will be understood that the cylindrical portion 44 of stop member 39 extends axially of the coil 10 to substantially the central zone thereof in order to limit the upward stroke of the plunger 36 to the area in which the magnetic flux density is greatest. Thus, preferably, the working gap 4 1 is provided approximately where flux density is greatest.

The configuration of the lower end 65 of the plunger 36 is designed to conform to the particular use of the solenoid. As stated above, it has been the practice in the past to make the axially extending sleeve disposed between the coil and plunger of non-magnetic material. However, in the illustrated embodiment of my invention the sleeve 22 is preferably made of a magnetic material, but this is not essential to the invention; it reduces the reluctance to magnetic force being applied to the plunger.

In order to properly align a solenoid plunger during reciprocation it has been necessary to provide an axially extending sleeve which, as stated above, has in the past, extended up to the stop or plug member. Thus, in known constructions, electromagnetic forces applied to the plunger are transmitted through the axially uniform cross sectional area of the plunger. 1 have discovered that by shortening the sleeve and providing the enlarged head in a working gap 41 at the zone of maximum flux density genenally at the center of the magnetic coil 10, there is a substantial increase in the pulling force per given plunger diameter exerted by the electromagnetic forces of coil 10 at a given voltage, because of the increased cross sectional area across which the lines of electromagnetic flux pass.

Thus, I have discovered a greatly improved solenoid construction which is very economically and simply manufactured with the additional advantage of eliminating accidental displacement of the plunger from the sleeve during packing, unpacking, or assembly with other apparatus.

While there has been shown and described the preferred form of mechanism of this invention it will be apparent that various modifications and changes may be made therein particularly in the form and relation of parts, without departing from the spirit of this invention as set forth in the appended claims.

I claim:

1. A solenoid comprising,

(a) a magnetic coil having a central opening extending axially thereof,

(b) a plunger having an enlarged in cross section head portion received in said coil opening and having a smaller in cross section body portion,

(c) means in said opening slidably embracing said smaller body portion of said plunger for axially aligning said plunger during reciprocation thereof, and

(d) means for confining the stroke of said enlarged head portion to substantially the zone of the greatest magnetic flux density of said solenoid along said opening.

'2. A solenoid comprising,

(a) a magnetic coil having a central opening extending axially thereof,

(b) a plunger having an enlarged substantially solid in cross section head portion received in said coil opening and having a smaller in cross section body portion terminating in -a working end outside of said opening,

(c) means in said opening slidably embracing said smaller body portion of said plunger for axially aligning said plunger during reciprocation thereof, and

(d) means for confining the stroke of said enlarged head portion to substantially the zone of the greatest magnetic flux density of said solenoid along said opening.

3. A solenoid comprising (a) a magnetic coil having a central opening extending axially therethrough and embracing the hereinafter claimed sleeve,

(b) a plunger having an enlarged diameter portion received in said coil opening and having a smaller in diameter body portion,

(c) stop means in said opening for limiting the travel of said plunger at one end and extending only to substantially the zone of greatest magnetic flux density of said solenoid along said opening, and

(d) a sleeve slidably embracing said smaller body portion, said sleeve extending axially into said opening to define a working gap between the internally disposed end thereof and said stop means, said plunger head being reciprocal in said Working gap and the outer diameter of said enlarged portion of said plunger being adjacent the inside diameter of said coil along said working gap.

4. A solenoid comprising (a) a magnetic coil having a central opening extending axially therethrough,

(b) a plunger having an enlarged diameter portion received in said coil opening and having a smaller in diameter body portion,

(c) a plunger stop closing one end of said opening and extending a selected distance to a zone of the greatest magnetic flux density of said solenoid along said opening,

(d) a cylindrical magnetic sleeve slidably embracing said smaller body portion of said plunger, said sleeve extending axially to said zone along said opening to define a working gap between said stop and the internally disposed end of said sleeve, in which gap said plunger head reciprocates.

5. A solenoid comprising (a) a magnetic coil having a central opening extending axially therethrough,

(b) a substantially solid in closs-section plunger having an enlarged diameter axially short portion received in said coil opening and having a smaller in diameter axially long body portion terminating in a working end outside of said opening.

(c) a plunger stop closing one one end of said opening and extending a selected distance to a zone of the greatest magnetic flux density of said solenoid along said opening,

(d) a sleeve slidably embracing said smaller body portion of said plunger, said sleeve extending axially to said zone along said opening to define a working gap at said zone between said stop and an internally disposed end of said sleeve, in which gap said plunger head reciprocates.

6. In combination with a solenoid construction having a magnetic coil with a central opening extending axially thereof,

(a) a substantially solid in cross-section plunger having an enlarged in cross-section head portion received solely in said coil opening and having a smaller in cross-section body portion terminating in a working end,

(b) means in said opening slidably embracing said smalled body portion of said plunger for axially aligning said plunger during reciprocation thereof, and

(c) means for limiting the axial travel of said plunger head portion to a selected working zone along said opening.

7. In combination with a solenoid construction having a magnetic coil with a central opening extending axially thereof,

(a) a substantially solid in cross-section plunger having an enlarged in cross-section head portion received solely in said coil opening and having a smaller in cross-section body portion received in said coil opening and terminating in a working end outside of said opening, and

(b) means in said opening for embracing and axially aligning said plunger during reciprocation thereof.

8. In combination with a solenoid construction having a magnetic coil with a central opening extending axially thereof,

(a) a plunger having an enlarged in cross-section head portion received solely in said coil opening and having a smaller in cross-section body portion, and (b) means for confining the stroke of said enlarged head portion to substantially the zone of great- 5 est magnetic flux density of said solenoid along said opening, and (0) means in said opening for embracing and axially aligning said plunger during rciprocation thereof. 9. In combination with a solenoid construction hav- 10 ing a magnetic coil with a central opening extending axially thereof,

(a) a substantially solid in cross-section plunger having an enlarged in cross-section head portion receively solely in said coil opening and having a smaller in cross'section body portion terminating in a working end outside of said opening,

(1)) means in said opening slidably embracing said smaller body portion of said plunger for axially aligning said plunger during reciprocation thereof,

and

(0) means for limiting the axial travel of said plunger head portion to a selected working zone along said opening.

References Cited by the Examiner UNITED STATES PATENTS 2,405,396 8/1946 Bazley 317191 2,698,404 12/1954 Edwards 317-191 2,985,802 5/1961 Drenning 3l7191 3,168,242 2/1965 Diener 317-199 X OTHER REFERENCES 544,464 4/1942 Great Britain. 689,295 3/1953 Great Britain.

ROBERT K. SCHAEFER, Acting Primary Examiner.

JOHN F. BURNS, BERNARD A. GILHEANY,

Examiners. 

1. A SOLENOID COMPRISING, (A) A MAGNETIC COIL HAVING A CENTRAL OPENING EXTENDING AXIALLY THEREOF, (B) A PLUNGER HAVING AN ENLARGED IN CROSS SECTION HEAD PORTION RECEIVED IN SAID COIL OPENING AND HAVING A SMALLER IN CROSS SECTION BODY PORTION, (C) MEANS IN SAID OPENING SLIDABLY EMBRACING SAID SMALLER BODY PORTION OF SAID PLUNGER FOR AXIALLY ALIGNING SAID PLUNGER DURING RECIPROCATION THEREOF, AND (D) MEANS FOR CONFINING THE STROKE OF SAID ENLARGED HEAD PORTION TO SUBSTANTIALLY THE ZONE OF THE GREATEST MAGNETIC FLUX DENSITY OF SAID SOLENOID ALONG SAID OPENING. 